This is pasted from Section IX, of the majority opinion in Roe v. Wade:
"All this, together with our observation, supra, that throughout the major portion of the 19th century prevailing legal abortion practices were far freer than they are today, persuades us that the word "person," as used in the Fourteenth Amendment, does not include the unborn."
http://caselaw.findlaw.com/us-supreme-court/410/113.html
At least in the context of abortion, the unborn are not persons with 14th Amendment Constitutional rights. I'm not a lawyer, but I don't think this precludes a state from considering a fetus as a person in other situations. Like if a pregnant woman is assaulted, and suffers a miscarriage as a result, a state can bring a homicide (I think feticide might be a better term) charge against the perp. But a properly done abortion, to which she gives consent, is not a crime. I can understand how this may seem contradictory, but nothing says that every law in all jurisdictions must be perfectly consistent.